1. Field of the Invention
The present invention generally relates to a touch system, and more particularly to a signal transmit channel integrate with electrostatic discharge (ESD) protection.
2. Description of Related Art
A touch panel may be combined with a display screen to result in a touch screen, which has been widely used as an input interface of an electronic device for detecting a touch input within a display area. The touch technology utilized in the touch panel may, for example, capacitive, resistive or optical.
Static electricity of human body or machine into an integrated circuit may generate large transient current that damages the integrated circuit. Electrostatic discharge (ESD) protection is thus an essential and important function for the integrated circuits. As the surface of a touch panel is frequently subjected to finger touch, it thus needs ESD protection capability to ensure normal operation of the touch panel.
FIG. 1 shows a circuit diagram illustrating a signal transmit (TX) channel 200 of a conventional touch control integrated circuit integrated with ESD protection circuit 20. A transmit signal is allowed to pass one signal transmit channel to an output end TXn at a time in order to drive a touch panel (not shown). When a scanning signal Sn closes a switch W and an inverted scanning signal SBn turns off a transistor Ms0, the transmit signal reaches the output end TXn. Alternatively, when the scanning signal Sn opens the switch W and the inverted scanning signal SBn turns on the transistor Ms0, the transmit signal is blocked from the output end TXn. When the transistor Ms0 is turned on, the transistor Ms0 should be a large-size device, which requires large circuit area and manufacture cost, in order to pull down the output end TXn to ground. Moreover, as the transistor Ms0 lies in an ESD path, it is liable to ESD damage.
Therefore, a need has arisen to propose a novel touch control circuit integrated with ESD protection to improve disadvantages of conventional touch control circuits.